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Effect of Polyelectrolyte Structure on Protein-Polyelectrolyte Coacervates: Coacervates of Bovine Se
閱讀：322 發(fā)布時(shí)間：2015-1-27| 提 供 商 | 美國(guó)布魯克海文儀器公司 | 資料大小 | 966.6KB |
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Electrostatic interactions between synthetic polyelectrolytes and proteins can lead to the formation of dense,
macroion-rich liquid phases, with equilibrium microheterogeneities on length scales up to hundreds of nanometers.
The effects of pH and ionic strength on the rheological and optical properties of these coacervates indicate
microstructures sensitive to protein-polyelectrolyte interactions. We report here on the properties of coacervates
obtained for bovine serum albumin (BSA) with the biopolyelectrolyte chitosan and find remarkable differences
relative to coacervates obtained for BSA with poly(diallyldimethylammonium chloride) (PDADMAC). Coacervation
with chitosan occurs more readily than with PDADMAC. Viscosities of coacervates obtained with chitosan are
more than an order of magnitude larger and, unlike those with PDADMAC, show temperature and shear rate
dependence. For the coacervates with chitosan, a fast relaxation time in dynamic light scattering, attributable to
relatively unrestricted protein diffusion in both systems, is diminished in intensity by a factor of 3-4, and the
consequent dominance by slow modes is accompanied by a more heterogeneous array of slow apparent diffusivities.
In place of a small-angle neutron scattering Guinier region in the vicinity of 0.004 Å-1, a 10-fold increase in
scattering intensity is observed at lower q. Taken together, these results confirm the presence of dense domains
on length scales of hundreds of nanometers to micrometers, which in coacervates prepared with chitosan are less
solidlike, more interconnected, and occupy a larger volume fraction. The differences in properties are thus correlated
with differences in mesophase structure.